川中大安寨段致密灰岩储层核磁共振T_2谱特征与解析  

Characterization and evaluation of NMR T_2 spectrum of the tight limestone reservoir in the Daanzhai Formation,Central Sichuan Basin

作　　者：李扬[1] 张凤生 李建玉 刘波[3] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国石油测井有限公司油气评价中心,陕西西安710077 [3]北京大学地球与空间科学学院,北京100871

出　　处：《油气地质与采收率》2017年第1期11-18,42,共9页Petroleum Geology and Recovery Efficiency

基　　金：国家自然科学基金项目"深部碳酸盐岩油气储层原位溶蚀模拟实验研究"(41272137)

摘　　要：川中大安寨段致密灰岩储层是致密油发育的重要层位。大安寨段致密灰岩储层为特低孔、特低渗透储层,发育微米级和纳米级孔隙。对研究区30块岩心样品进行饱和水核磁共振T_2谱测量,结果表明,其核磁共振T_2谱特征表现为单峰、双峰(左峰占优和右峰占优)和近似三峰4种类型。综合分析孔隙分量与储层渗透率的关系以及岩石微观孔隙特征发现,研究区具有核磁共振T_2谱单峰特征的岩心样品主要发育纳米级孔隙,且渗透率较低。当核磁共振T_2谱峰值向短弛豫时间方向移动时,若发育连通性好的晶间孔、延伸较远的晶间缝和粘土矿物层间孔,则储层表现为较好的渗透性,且较大级别孔隙分量与渗透率的相关性变好;当核磁共振T_2谱峰值向长弛豫时间方向移动时,若壳间孔和晶间孔局部发育、晶间缝或介壳层间缝延伸长度较小,则储层的渗透率较低,且较大级别孔隙分量与渗透率的相关性变差。微米级构造缝、晶间缝对储层渗透性具有明显的改善作用。The tight limestone in Jurassic Daanzhai Formation of Central Sichuan Basin is one of the most important tight oil reservoirs in China. The Daanzhai Formation is considered as ultra-low porosity and permeability reservoir with nanometer and micrometer pores and fractures. A total of thirty core plugs were saturated with saline water for days,and then nuclear magnetic resonance(NMR)T_2 measurement was conducted. The results obtained show that there are four types of peak distribution patterns for NMR T_2 spectrum,including unimodal distribution,bimodal distribution(dominated either by left peak or right peak)and pseudo triple-modal distribution. It is found that core samples with unimodal NMR T_2 spectrum are characterized by nanometer pores with low permeability through comprehensive analysis of the statistic relationship between pore components and reservoir permeability and the microscopic characteristic of pores. Although T_2 spectrum distribution shifts to short relaxation time,the permeability value can be high with a good relationship between components of larger pores and flowing capacity when connected intercrystal pores,extended intercrystal fractures and inter-layer pores within clay minerals develop well. When the T_2 spectrum distribution shifts to long relaxation time,the permeability valuecan be low with a weak relationship between components of larger pores and flowing capacity if inter-shell and intercrystal pores are locally developed and intercrystal fractures or inter-layer fractures within shells has limited length. The micronscale fractures such as structural fractures and intercrystal fractures contribute to the increase of reservoirs permeability obviously.

关 键 词：大安寨段 致密油储层 核磁共振T2谱 孔隙结构 四川盆地 

分 类 号：P631.823[天文地球—地质矿产勘探]